for debug, plot the line 10% to upTrend
upTrendLine = direction < 0 ? supertrend : na
upTrend10 = upTrendLine * 1.1
plot(upTrend10)
Now create the alert
croosUpTrend10 = ta.crossunder(low, upTrend10)
plotshape(croosUpTrend10)
alertcondition(croosUpTrend10, "croosUpTrend10" )